This is the fourth in a four-part series on tropical cyclones, beginning with Windy Changes, on last year’s Typhoon Haiyan and continuing with Data of Hurricanes Past and Problems with Hurricanes Present. Note that “tropical cyclone” is a catchall term that includes tropical storms, hurricanes, and typhoons. I have not repeated reference links from the previous post.
The Atlantic Ocean is quiet at present. So is the Eastern Pacific. The National Hurricane Center (NHC) does not expect any tropical cyclone activity in either basin within the next 48 hours.
The Western Pacific is different, currently sporting two storms, the as-yet-unnamed Tropical Depression Ten and Typhoon Rammasun. TD Ten is predicted to become a tropical storm (and receive a name) sometime today or tomorrow and to become at least a Category 1 typhoon sometime next week. Typhoon Rammasun has already hit the Philippines and is currently intensifying. It could become a Category 4 storm later today and is expected to hit Vietnam and China Friday and Saturday (since the Philippines have their own system of naming storms, the typhoon was called Glenda there. I have been unable to find a reliable damage report yet).
The Atlantic hurricane season was predicted to be mild. The Western Pacific Typhoon Season was predicted to be just above normal, but with more intense typhoons because of a developing El Niño. Although the characteristic atmospheric pattern hasn’t formed yet, so there is no El Niño yet, the Pacific is unusually warm, consistent with El Niño formation. So, this season is shaping up as predicted so far.
But what about tropical cyclones farther out? Next year or the year beyond? Or ten or twenty years out?
Common sense dictates that because these storms feed on warm water, global warming should make them worse. Indeed, with every monster storm that roars into the news, global warming gets easier to believe.
However, problems with historical storm data make it very hard to tell whether tropical cyclones have been getting worse because of climate change so far. Because “bad” storms are not necessarily the most intense meteorologically, it’s even hard to say what “getting worse” means. Looking into the future is similarly difficult.
The climate system as a whole is very complex. Besides warm water, tropical cyclones also require reduced wind shear and other atmospheric patterns. If wind shear increases due to climate change, then there will be fewer tropical cyclones even as the weather warms. Other possibilities are that the number of storms could stay about the same but the intensity could increase, or that the storm tracks could change and bring typical storms into atypical areas.
Different storm basins can respond in different ways, too.
Scientists make predictions about what is going to happen using computer models. The basic idea is that a computer simulation capable of recreating changes in the past can also show what will happen under certain conditions in the future.
But no computer simulation can represent the full complexity of the real world; The Matrix is still very much fiction. Computer models posit a simplified version of the world and they therefore have limitations. When scientists use a model, they generally understand those limitations fairly well. Models are useful because scientists know how to ask questions the model can handle and they know how to put the results in context. But we aren’t at the point where a computer can tell us what will happen.
Computer can give us pictures of the range of possibility.
I have read a number of different predictions, including the summary by the IPCC, and I have not yet found one that predicts a dramatic increase in both frequency and wind intensity of tropical cyclones all over the world.
Instead, many show the total number of tropical cyclones not changing very much, but the proportion of Category 4 and 5 storms increasing, all over the world. NOAA’s version of this prediction warns that there is so much variation from year to year that the difference might not be evident for many decades–the old problem of finding the signal within the noise.
NOAA does not point out that this doesn’t mean there has been no change yet. Indeed, another study shows that there has been a significant increase in storm power in some ocean basins already.
NOAA’s prediction adds that tropical cyclones are going to get rainier, and this is very bad news. We already know that the sea is rising, making storm surges worse. With storms also getting rainier, freshwater flooding is set to get worse, too. Since most people who die in tropical cyclones die of water, not wind, this means we’re looking at the deadly parts of the storm getting worse.
A separate NOAA study shows storm tracks have been changing, moving further into the temperate zones more often. This means more storm surges and more flooding in areas not prepared for big storms, worldwide. How many times can the bridges in Vermont be rebuilt? How long till Boston and Portland join the list of cities filled with FEMA trailers?
The question is, what greenhouse gas emissions were these predictions based on? Do we still have time to not create these scenarios?
The present is the future’s past.